Does Mac-Os come with a client to connect to exchange.
If not, is Outlook 2007 available for Mac-Os?
The is a way to connect to exchange from OS X for both calendar and email - both for SNow Leopard and the older OSs.
I have used both email and calendar from exchange on the Mac. The presentation is in the "Apple Way" that is quite different than Outlook. There are two separate programs, Mail and Calendar, vs the unified organizer that Outlook is supposed to be (or fails to be, depending on your view)
The existing Mac Office has Entourage. Microsoft recently release Entourage Web Services Edition, which is kinda an Outlook client and syncs both with Exchange and Sharepoint.
The next release of Office, due later this year, will have a full Mac Outlook client that is on peer with the Windows version.
Mail.app and iCal and Address Book can connect to exchange servers out of the box in snow Leopard.
Outlook was supposedly going to come to OS X but I haven't heard anything about it in a while.